Radiometric Tissue Contact and Tissue Type Detection

This application is a continuation of U.S. patent application Ser. No. 15/527,924, filed Nov. 18, 2015, which is a § 371 national-phase of International Patent Application No. PCT/US2015/061347, filed May 18, 2017, which claims priority to U.S. Provisional Application No. 62/081,697 filed Nov. 19, 2014; to U.S. Provisional Application No. 62/087,678 filed Dec. 4, 2014; and to U.S. Provisional Application No. 62/105,366 filed Jan. 20, 2015, the entire contents of each of which are incorporated herein by reference in their entirety.

Tissue ablation may be used to treat a variety of clinical disorders. For example, tissue ablation may be used to treat cardiac arrhythmias by destroying (for example, at least partially or completely ablating, interrupting, inhibiting, terminating conduction of, otherwise affecting, etc.) aberrant pathways that would otherwise conduct abnormal electrical signals to the heart muscle. Several ablation techniques have been developed, including cryoablation, microwave ablation, radio frequency (RF) ablation, and high frequency ultrasound ablation. For cardiac applications, such techniques are typically performed by a clinician who introduces a catheter having an ablative tip to the endocardium via the venous vasculature, positions the ablative tip adjacent to what the clinician believes to be an appropriate region of the endocardium based on tactile feedback, mapping electrocardiogram (ECG) signals, anatomy, and/or fluoroscopic imaging, actuates flow of an irrigant to cool the surface of the selected region, and then actuates the ablative tip for a period of time and at a power believed sufficient to destroy tissue in the selected region.

Medical microwave radiometry utilizes temperature dependent microwave radiation from tissue to non-invasively monitor thermal ablation procedures. The radiation is received by an antenna and the antenna receiving pattern determines the volume of tissue that is being characterized by the radiometer. In general, the frequency of the radiometer system will determine the volume of tissue being measured, with lower frequencies tending to correspond to a larger volume due to a greater penetration depth (lower conductivity) in tissue.

In accordance with one embodiment, a system for facilitating determination of quality of contact between an energy delivery member and tissue prior to and during energy delivery includes a processor configured to receive an output signal from a radiometer carried by an energy delivery member; and to determine a level of tissue contact between the energy delivery member and tissue based, at least in part, upon the variability of the output signal. The determination of the level of tissue contact may optionally be based, at least in part, on a moving average of the output signal (radiometric response) and/or a variability index determined by subtracting the moving average from the output signal (radiometric response). The processor may optionally be configured to cause an indicator (color and/or textual information) of the level of tissue contact to be displayed on a display. The embodiment of the system may optionally include a single radiometer. The embodiment of the system may include a single energy delivery member and not multiple energy delivery members.

In accordance with several embodiments, a system for facilitating determination of quality of contact between an energy delivery device and tissue prior to and during energy delivery comprises a radiometer configured to be coupled to a processor. In several embodiments, the processor is specifically configured to execute computer-readable instructions stored in a non-transitory computer readable medium to provide an output (for example, qualitative or quantitative assessment) indicative of tissue contact based on a radiometric response (for example, output signal) received from the radiometer. The processor may also be configured to determine a level of tissue contact between a distal tip of the energy delivery device and targeted tissue to be ablated or otherwise treated based, at least in part, upon said output. In some embodiments, the processor is further configured to cause an indicator of the level of tissue contact to be displayed on a display (for example, a generator display). The various functions may be performed by software modules executed by the processor and stored in memory. In some embodiments, the output is based, at least in part, on a moving average of the radiometric response (for example, a 5-point moving average). In one embodiment, the output comprises a variability index determined by subtracting the moving average from the raw radiometric output signal (for example, voltage signal). The output may be configured to be output on the display to provide user feedback regarding contact detection and assessment.

The indicator may comprise a color (for example, red for poor or weak contact, yellow for questionable or medium contact, and green for good or strong contact). In some embodiments, the indicator comprises textual or graphical information indicative of the level of tissue contact, or indicative of whether contact is achieved or not. For example, a checkmark may appear to indicate that contact has occurred or that the contact is excellent or very strong. The indicator may automatically cause an energy delivery module to enter an energy delivery mode or may signal to a user that it is safe to initiate delivery of energy to the targeted tissue. In some embodiments, the output comprises an audible indication of contact or level of contact.

In some embodiments, the level of tissue contact is determined based upon a comparison to at least one threshold. The at least one threshold may comprise contact vs. no-contact threshold or a piecewise linear threshold to indicate gradual contact (for example, poor=>medium=>good=>excellent). Each qualitative contact assessment category may be indicated by a different color or other indicator. In some embodiments, the amount of contact may be provided as a quantitative assessment (for example, a percentage of electrode surface area covered).

In some embodiments, the at least one threshold is configured to be automatically adjusted based on historical variability information data. The automatic adjustment may be based on an auto-scaling function. The level of tissue contact can be selected from one of: poor contact, medium contact, good contact, and excellent contact, wherein different levels of tissue contact are displayed using different colors. Any number of qualitative indicators may be used.

In some embodiments, the processor is configured to provide an output indicative of a level of cardiac tissue contact based on raw radiometer data received from the radiometer. In one embodiment, the output is based on filtering of the radiometric response with a moving average filter. In accordance with several embodiments, the output is not substantially affected by the type of cardiac or other tissue being contacted.

In some embodiments, the system comprises or consists essentially of a radiofrequency energy generator having a display. The display may be configured to display a user interface that is configured to receive user input and display output for the user to observe. The user interface may include a touchscreen interface. The system may comprise or consist essentially of an energy source or supply (for example, RF generator) comprising one or more energy delivery members or elements (for example, RF electrodes) configured to deliver energy (such as ablative RF energy) provided by the energy source or supply.

In some embodiments, the processor is configured to extract variability information from a signal received from the radiometer, determine a level of tissue contact between a distal tip of the energy delivery device and tissue to be ablated based, at least in part, upon the variability information, and/or cause an output indicative of the level of tissue contact to be displayed on the display of the energy source. In one embodiment, the variability information is based on a moving average of the signal received from the radiometer. The determination based upon extraction of variability information may provide increased confidence that contact has been achieved over determinations based on the raw radiometer output signal. In some embodiments, the output is not substantially affected by the type of tissue being contacted.

In accordance with several embodiments, a method of determining contact between an energy delivery device and tissue prior to and during energy delivery comprises receiving an output signal from a radiometer. The contact determination may be provided without delivering any ablative energy and prior to delivery of ablative energy. In one embodiment, the method comprises or consists essentially of extracting variability information from the output signal of the radiometer and causing an output indicative of the variability information to be displayed on a display. The method may also comprise determining a level of tissue contact based, at least in part, on the variability information. The variability information may comprise a variability index determined by subtracting a moving average (for example, a 5-point moving average) from the output signal (such as voltage signal) of the radiometer. In some embodiments, the output to be displayed comprises a color indicative of the level of tissue contact. The output may comprise textual or graphical information, alone or in combination, and/or in combination with color indication information. In some embodiments, the output does not include textual information and is purely visual or graphical.

In some embodiments, a method of determining contact between an energy delivery device and tissue prior to and during energy delivery comprises receiving raw signal data (for example, voltage or temperature data) from a radiometer and determining a level of contact from the raw signal data by filtering the raw signal data with a moving average filter and then subtracting the moving average filter output from the raw signal data. In one embodiment, the method comprises causing an output indicative of quality of contact to be presented on a display based on the determined level of contact. The output, or indication, may comprise a color indicative of the quality of tissue contact (for example, red, yellow or green). The indication may also or alternatively comprise textual or quantitative (for example, percentage of total electrode contact) assessments. In various embodiments, the contact indication is purely qualitative and/or purely graphical or visual (without text).

In some embodiments, a method of determining contact between an energy delivery device and tissue prior to and during energy delivery comprises receiving raw signal data from a radiometer indicative of an amount of tissue contact and providing an output indicative of a qualitative assessment of a level of tissue contact based on the received radiometer data. Providing an output indicative of a qualitative assessment of a level of tissue contact may comprise filtering the raw signal data to isolate variability information using one or more filters implemented in hardware and/or software. In one embodiment, the method comprises causing the output to be displayed on a display.

In accordance with several embodiments, a system for facilitating determination of quality of contact between an energy delivery member of a medical instrument and tissue during an energy delivery procedure comprises a processor configured to receive an output signal from a radiometer carried by the medical instrument, to determine whether a variability in the output signal is within a threshold range, and to generate an action signal to cause an action if the variability in the output signal is outside of the threshold range. The threshold range may be a predetermined range of expected variability. The variability determination may be performed by calculating a slope of at least a portion of the output signal from the radiometer. The variability determination may be continuously performed at a regular (for example, periodic) interval. In various embodiments, the interval is between 0.1 and 2 seconds (for example, between 0.1 and 0.5 seconds, between 0.5 seconds and 1 second, between 1 second and 2 seconds, between 1 second and 1.5 seconds, between 0.1 and 1 second, between 0.5 and 1.5 seconds, and overlapping ranges thereof). In some embodiments, the action may be a user alert (for example, an audible or visual warning). In some embodiments, the action may be automatic termination of energy delivery by the energy delivery member of the medical instrument. In other embodiments, the action comprises an adjustment to one or more parameters of the energy delivery.

In accordance with several embodiments, a method of monitoring contact between an energy delivery member of a medical instrument and target tissue being treated comprises receiving an output signal from a radiometer of the medical instrument while the energy delivery member is delivering energy, determining a variability of the output signal, identifying whether the variability is within a threshold range and generating an action configured to alter the energy delivery by the energy delivery member when the variability is identified as being outside the threshold range. In some embodiments, the action comprises a user alert, such as an audible warning or a visual warning that is output on a display. In some embodiments, the action comprises automatic termination of the energy delivery or adjusting one or more parameters of the energy delivery. Determining the variability may comprise calculating a slope of at least a portion of the output signal from the radiometer. This calculation of slope may occur at a periodic interval. In one embodiment, the periodic interval is between 0.1 and 2 seconds.

In accordance with several embodiments, a system for determining tissue type using a reflectometer includes a tissue heating device (for example, ablation catheter) and a processor. The tissue heating device may include an elongate body having a proximal end and a distal end. An antenna may be positioned at the distal end of the elongate body. In one embodiment, a radiofrequency electrode is positioned at the distal end of the elongate body adapted to contact tissue of a subject and to deliver radiofrequency energy sufficient to heat (for example, ablate) the tissue. In one embodiment, the tissue heating device includes a radiometer positioned at the distal end of the elongate body. The radiometer may be configured to determine temperature at a depth from a surface of the tissue. In several embodiments, the tissue is cardiac tissue; however, other tissue may also be treated (for example, tissue of other organs or vessel walls).

In one embodiment, the heating device includes a miniaturized reflectometer positioned at the distal end of the elongate body. The reflectometer may advantageously be configured to directly measure (for example, determine, calculate) an amount of reflected power received from the antenna. In some embodiments, the reflected power received from the antenna may be filtered by a band-stop filter to avoid frequencies in an operating bandwidth of the radiometer, thereby reducing the likelihood of interference with the operation of the radiometer. In some embodiments, the radiometer is switched to a reference mode while the reflectometer is switched to the antenna.

A processor, controller or other computing device(s) is configured to determine a reflection coefficient of the reflected power and to identify a type of tissue based on the determined reflection coefficient. The reflectometer may be used to determine both the magnitude and phase of the reflection coefficient. The reflection coefficient may be determined at an operating frequency within an operating band of the radiometer (for example, at an operating frequency of the radiometer, such as 4 GHz) or at multiple frequencies outside the operating band of the radiometer and then interpolated using averaging circuits, filters or methods (digital and/or analog).

In some embodiments, the processor is further configured to determine whether the distal end of the elongate body is in contact with a target tissue to be heated (for example, ablated) based on the determined tissue type. The determined tissue type may, for example, provide information regarding whether an ablation procedure at a target ablation site has been successful. The processor may also execute a code module or set of instructions to automatically adjust or calibrate temperature measurements obtained by the radiometer based, at least in part, on the reflection coefficient measured, calculated or otherwise determined by the reflectometer, thereby enhancing operation of the radiometer.

The type of tissue identified by the processor may be, for example, non-ablated normal tissue, infarct tissue, or ablated tissue. The identified tissue type may provide confirmation of a successful ablation or an indication that the ablation was not effective and additional ablation time is required. The tissue may be cardiac tissue or tissue of other organs or vessels. In some embodiments, the tissue type may be determined to be blood or a tissue wall to facilitate determination of contact prior to ablation.

In some embodiments, the processor is configured to provide an output indicative of the tissue type and/or an output indicative of contact with tissue. For example, the output can indicate that contact has occurred or can provide a qualitative assessment of the level of contact (for example, excellent, good, poor, no contact). In various embodiments, the output indicative of tissue type may comprise a live reading of the reflection coefficient magnitude plotted as a bar graph or a live reading of the magnitude and phase of the reflection coefficient plotted on a Smith chart or polar plot. The output may be displayed on a display in communication with the processor. For example, in one embodiment, the output is displayed on a display of an energy delivery module (for example, a generator).

In some implementations, the reflectometer is configured to determine reflection coefficients at multiple frequencies outside the operation bandwidth of the radiometer and the processor is configured to determine a reflection coefficient at an operating frequency of the radiometer based on interpolation using the determined reflection coefficients at said multiple frequencies. As one example, if the radiometer is designed to operate at a frequency of 4 GHZ, the reflectometer may determine reflection coefficients at 3 GHz and 5 GHz and then estimate the reflection coefficient at 4 GHz through interpolation techniques (for example, using an averaging circuit). Two or more frequencies may be used (for example, 2, 3, 4 or more).

In accordance with one embodiment, a cardiac ablation catheter comprises or consists essentially of an elongate body having a proximal end and a distal end, an antenna positioned at the distal end of the elongate body, a radiofrequency electrode positioned at the distal end of the elongate body adapted to contact tissue of a subject and to deliver radiofrequency energy sufficient to ablate the tissue, a radiometer positioned at the distal end of the elongate body and a miniaturized reflectometer positioned at the distal end of the elongate body. The radiometer is configured to determine temperature at a depth from a surface of cardiac tissue and the reflectometer is configured to determine a reflection coefficient based on an amount of reflected power received from the antenna. In one embodiment, the radiometer is switched to a reference mode while the reflectometer is switched to the antenna. In one embodiment, the reflected power received from the antenna is filtered by a band-stop filter to avoid frequencies in an operating bandwidth of the radiometer.

In accordance with several embodiments, a system for determining tissue type using a reflectometer comprises a means for connecting (for example, an electrical, mechanical, or electromechanical interface or input/output port) to a tissue ablation device comprising an antenna, an ablation element configured to contact tissue of a subject and to deliver energy or fluid sufficient to ablate the tissue, a radiometer and a miniaturized reflectometer configured to determine an amount of reflected power received from the antenna. The system also comprises a processor configured to determine a reflection coefficient of the reflected power and to determine a tissue type based on the reflection coefficient. The reflected power received from the antenna may be filtered by a band-stop filter to avoid frequencies in an operating bandwidth of the radiometer. In one embodiment, the radiometer is switched to reference mode while the reflectometer is switched to the antenna.

In accordance with several embodiments, a method of determining tissue type using a reflectometer within a radiometric ablation catheter or other tissue treatment device includes receiving power from an antenna of the radiometric ablation catheter. In some implementations, an impedance matching circuit or network is positioned between the antenna of the radiometric ablation catheter and the reflectometer circuit. The radiometer, in normal operation, switches back and forth between a reference mode and a measurement mode for calibration purposes. Accordingly, in some implementations, a switch is provided to switch the power that is normally directed to the radiometer to instead be directed to the reflectometer for performing reflection coefficient measurements or calculations while the radiometer is switched to a reference load. The switching may be controlled by one or more clocks. The method may include measuring, calculating or determining a reflection coefficient of the power using the reflectometer. The reflectometer may measure both the magnitude and phase of the reflection coefficients. In some embodiments, the method includes determining a tissue type based on the calculated or measured reflection coefficient.

In accordance with several embodiments, the method includes determining whether the ablation catheter is in contact with a target tissue to be ablated based on the determined tissue type and/or confirming whether an ablation procedure has been successful (or proving other feedback related to a tissue treatment procedure) based on the determined tissue type. In some implementations, the method advantageously includes automatically adjusting temperature measurements obtained by the radiometer based on the calculated reflection coefficient, thereby enhancing operation of the radiometer.

The method may also include generating an output indicative of the tissue type and/or tissue contact. The output indicative of contact may indicate whether or not contact has occurred or may indicate a level or quality of contact. In some implementations, the method includes displaying the output on a display of an energy delivery module (for example, a radiofrequency generator). The method may include interpolating between the reflection coefficients determined at multiple frequencies to estimate a reflection coefficient at the operating frequency of the radiometer.

In accordance with several embodiments, a method of determining tissue type using a reflectometer within a radiometric ablation catheter comprises filtering a reflectometer signal with a band-stop filter to avoid frequencies in an operating bandwidth of the radiometer, calculating a reflection coefficient of the power using a reflectometer; and determining a tissue type based on the calculated reflection coefficient. The reflection coefficient may be calculated by a processor based on an amount of power received by the reflectometer (for example, from an antenna of the radiometric ablation catheter). The tissue type determination and filtering may also be performed by the processor or other computing device(s). In some embodiments, the method comprises determining whether the ablation catheter is in contact with a target tissue to be ablated and/or confirming whether an ablation procedure has been successful based, at least in part, on the determined tissue type.

In some embodiments, the method comprises automatically adjusting temperature measurements obtained by the radiometer based on the calculated reflection coefficient. In some embodiments, the method comprises generating an output indicative of the tissue type and/or contact. The output indicative of contact may comprise an indication that contact has occurred or an indication of a level or quality of contact. In some embodiments, the method comprises displaying the output on a display of an energy delivery module (for example, a generator). In some embodiments, calculating a reflection coefficient of the power using a reflectometer comprises determining a magnitude and a phase of the reflection coefficient.

In some embodiments, the reflectometer is configured to determine reflection coefficients with respect to a reference load by utilizing a Dicke switch concept in which the input of the reflectometer is switched between the antenna and a reference load- and the output signal is fed into a synchronous detector circuit.

In accordance with several embodiments, a medical instrument for facilitating deeper temperature measurements by a radiometer comprises utilizing a higher frequency for the radiometer circuitry than the frequency of the antenna, or conversely comprises utilizing an antenna that is configured to operate at a frequency that is lower than an operational frequency (e.g., center frequency) of the radiometer circuitry. In some embodiments, the medical instrument does not require changing the operational frequency of the radiometer or replacing the radiometer with a lower-frequency radiometer. The medical instrument may comprise or consist essentially of an antenna and a radiometer or radiometer circuitry. In some embodiments, the medical instrument comprises a transition network (e.g., matching circuit) positioned between the antenna and the radiometer and/or a frequency multiplier configured to (a) amplify an output signal from the antenna or transition network and (b) increase (e.g., multiply) a frequency of the output signal from the antenna or transition network to an operational frequency of the radiometer. In various embodiments, the medical instrument is a catheter configured to diagnose and/or treat tissue. As one example, the medical instrument is a radiometric cardiac ablation catheter configured for use in ablating endocardial tissue sufficient to treat cardiac arrhythmia or fibrillation.

In some embodiments, the antenna is configured to operate at a frequency that is a fraction (for example, one-fourth, one-third, one-half) of the operational frequency of the radiometer. The transition network may be configured to multiply (for example, double, triple or quadruple) the frequency of the output signal from the antenna. In some embodiments, the medical instrument further comprises an ablation member (for example, a radiofrequency electrode) configured to deliver ablative energy to tissue (for example, endocardial tissue). In one embodiment, the ablation member consists of a single member.

In some embodiments, the center frequency of the radiometer is 4 GHZ, corresponding to an operational frequency band of 3.6 GHz to 4.4 GHz. For such a center frequency, the antenna may be designed or tuned to receive signals having a center frequency of about 2 GHz, 1.33 GHz or 1 GHz and the transition network is configured to double, triple or quadruple the frequency of the signals received by the antenna before feeding them to the radiometer. In one embodiment, the medical instrument comprises a switch configured to switch input to the radiometer between the antenna and a reference load. The frequency multiplier may comprise an amplification component and a separate frequency multiplication component or the two components may be provided as a single integral component. In one embodiment, the transition network (for example, frequency multiplier) comprises a single stage (e.g., transistor) with input and output matching networks configured to provide a simultaneous match for low-noise amplification and frequency multiplication. In some embodiments, the low noise amplification component serves as the first gain stage of the radiometer circuit. Thus, the multiplication/transition stage and radiometer may be part of the same radiometer circuit.

In accordance with several embodiments, a non-invasive method for characterizing tissue or performing measurements of tissue at an increased depth is provided. In some embodiments, the method comprises receiving microwave energy from a target region using an antenna designed to receive microwaves having a frequency that is lower than an operational frequency of a radiometer using an antenna, increasing the frequency of the received microwave energy up to the operational frequency of the radiometer and outputting signals having the increased frequency to the radiometer, thereby facilitating measurements using the radiometer at increased depths compared to depths obtainable using frequencies within an operational frequency band of the radiometer. In some embodiments, the method comprises receiving microwave energy from a target region using an antenna designed to receive microwaves having a given frequency using an antenna, increasing the frequency of the received microwave energy up to a higher frequency, and utilizing the higher frequency signals in the radiometer, thereby facilitating the use of more spatially compact, higher frequency radiometer circuit implementations, and thereby allowing for space constraints within miniature ablation catheters.

In some embodiments, the operational frequency of the antenna is a fraction (for example, one-fourth, one-third, one-half) of the operational frequency of the radiometer. The step of increasing the frequency between the antenna to the radiometer may comprise multiplying the frequency (for example, doubling, tripling or quadrupling the frequency). The antenna, frequency multiplier, and radiometer may be positioned along a distal end of a cardiac ablation catheter, which may be configured to characterize, diagnose, and/or treat tissue at a depth.

In some embodiments, the method comprises amplifying the received microwave energy and/or filtering out noise from the received microwave energy. The method may comprise comprising determining tissue temperatures at a depth based on the signals output to the radiometer. In some embodiments, the method comprises determining tissue characteristics (for example, tissue type) based on the determined tissue temperatures. The tissue characteristics may be used for contact sensing, lesion volume or gap assessments, or treatment confirmation purposes. In some embodiments, delivery of energy or fluid to target tissue may be initiated, continued, adjusted or terminated based on tissue characteristics or other feedback determined by the radiometer in real time or substantially in real time from the output signals of the frequency multiplier, amplifier or transition network. For example, if it is determined that tissue has been sufficiently ablated, delivery of ablative energy or fluid may be terminated. As another example, if a lesion gap is detected or if it is determined that the tissue has not been sufficiently ablated, delivery of ablative energy or fluid may be adjusted (change in position of distal tip, change in orientation of distal tip, duration of delivery, power increase or decrease, irrigation or cooling increase or decrease, etc.) and/or continued.

In accordance with several embodiments, a method of facilitating temperature measurements of a radiometric system at increased depth without altering an operational frequency of a radiometer is provided. The method may comprise receiving electromagnetic energy from tissue using an antenna designed to receive electromagnetic energy having a frequency that is less than an operational frequency of the radiometer, increasing the frequency of the electromagnetic energy received by the antenna to the operational frequency of the radiometer and outputting signals having the increased frequency to the radiometer, thereby facilitating measurements using the radiometer at increased depths compared to depths obtainable using frequencies within an operational frequency band of the radiometer. In accordance with one embodiment, a method of facilitating temperature measurements of a radiometric system at a given depth while increasing the operational frequency of a radiometer comprises receiving electromagnetic energy at a given frequency, multiplying the frequency of the received electromagnetic emissions up to a higher frequency, and utilizing a higher frequency radiometer, thereby allowing spatially compact, high frequency circuit techniques to be utilized in the implementation of the radiometer circuit.

In some embodiments, the frequency of the antenna is a fraction of the operational frequency of the radiometer. In some embodiments, increasing the frequency comprises multiplying the frequency (for example, doubling, tripling or quadrupling the frequency). The method may comprise determining tissue temperatures at a depth based on the signals output to the radiometer and determining tissue characteristics (such as tissue type) based on the determined tissue temperatures.

In accordance with one embodiment, a method of facilitating temperature measurements of a radiometric system at increased depth without altering an operational frequency of a radiometer comprises receiving microwave energy from tissue using an antenna designed to receive microwaves having a frequency that is a fraction of an operational frequency of the radiometer, multiplying the frequency of the received microwave emissions up to the operational frequency of the radiometer and outputting signals having the multiplied frequency to the radiometer, thereby facilitating measurements using the radiometer at increased depths compared to depths obtainable using frequencies within an operational frequency band of the radiometer. In accordance with one embodiment, a method of facilitating temperature measurements of a radiometric system at a given depth while increasing the operational frequency of a radiometer comprises receiving microwave energy at a given frequency, multiplying the frequency of the received microwave emissions up to a higher frequency, and utilizing a higher frequency radiometer, thereby allowing spatially compact, high frequency circuit techniques to be utilized in the implementation of the radiometer circuit.

The methods summarized above and set forth in further detail below describe certain actions taken by a practitioner; however, it should be understood that they can also include the instruction of those actions by another party. For example, actions such as “positioning a distal tip of a catheter in contact with targeted tissue” include “instructing the positioning a distal tip of a catheter in contact with targeted tissue.” Further aspects of embodiments of the invention will be discussed in the following portions of the specification. With respect to the drawings, elements from one figure may be combined with elements from the other figures.

schematically illustrates one embodiment of an energy delivery systemthat is configured to selectively ablate or otherwise heat targeted tissue (for example, cardiac tissue, pulmonary vein, other vessels or organs, nerves, etc.). As shown, the systemcan include a medical instrumentcomprising one or more energy delivery members(for example, radiofrequency electrodes, ultrasound transducers, microwave antennas) along a distal end of the medical instrument. The medical instrument can be sized, shaped and/or otherwise configured to be passed intraluminally (for example, intravascularly) through a subject being treated. In other embodiments, the medical instrument is not positioned intravascularly but is positioned extravascularly via laparoscopic or open surgical procedures. In various embodiments, the medical instrumentcomprises a catheter, a shaft, a wire, and/or other elongate instrument. A radiometermay be included at the distal end of the medical instrument, or along its elongate shaft or in its handle. The term “distal end” does not necessarily mean the distal terminus or distal end. Distal end could mean the distal terminus or a location spaced from the distal terminus but generally at a distal end portion of the medical instrument.

In some embodiments, the medical instrumentis operatively coupled to one or more devices or components. For example, as depicted in, the medical instrumentcan be coupled to a delivery module(such as an energy delivery module). According to some arrangements, the energy delivery moduleincludes an energy generation devicethat is configured to selectively energize and/or otherwise activate the energy delivery member(s)(for example, radiofrequency electrodes) located along the medical instrument. In some embodiments, for instance, the energy generation devicecomprises a radiofrequency generator, an ultrasound energy source, a microwave energy source, a laser/light source, another type of energy source or generator, and the like, and combinations thereof. In other embodiments, energy generation deviceis substituted with or use in addition to a source of fluid, such a cryogenic fluid or other fluid that modulates temperature. Likewise, the delivery module (for example, delivery module), as used herein, can also be a cryogenic device or other device that is configured for thermal modulation. Radiometermay be configured to sense the temperature change of the targeted tissue in response to energy delivery or thermal modulation. The output of the radiometer(for example, the radiometric voltage (V)) may be passed back to the energy delivery module.

With continued reference to the schematic of, the energy delivery modulecan include one or more input/output devices or components, such as, for example, a touchscreen device, a screen or other display, a controller (for example, button, knob, switch, dial, etc.), keypad, mouse, joystick, trackpad, microphone or other input device and/or the like. Such devices can permit a physician or other user to enter information into and/or receive information from the system. In some embodiments, the output devicecan include a touchscreen or other display that provides tissue temperature information, contact information, other measurement information and/or other data or indicators that can be useful for regulating a particular treatment procedure.

According to some embodiments, the energy delivery moduleincludes a processor(for example, a processing or control unit) that is configured to regulate one or more aspects of the treatment system. The processormay include one or more conventional microprocessors that comprise hardware circuitry configured to read computer-executable instructions and to cause portions of the hardware circuitry to perform operations specifically defined by the circuitry. The output of radiometeris processed by processorso as to detect contact between delivery memberand tissue. The modulecan also comprise a memory unit or other storage device(for example, computer readable medium) that can be used to store operational parameters and/or other data related to the operation of the system. The storage devicemay include random access memory (“RAM”) for temporary storage of information and a read only memory (“ROM”) for permanent storage of information, which may store some or all of the computer-executable instructions prior to being communicated to the processorfor execution, and/or a mass storage device, such as a hard drive, diskette, CD-ROM drive, a DVD-ROM drive, or optical media storage device, that may store the computer-executable instructions for relatively long periods of time, including, for example, when the computer system is turned off.

The modules and sub-modules of the systemmay be connected using a standard based bus system. In different embodiments, the standard based bus system could be Peripheral Component Interconnect (“PCI”), Microchannel, Small Computer System Interface (“SCSI”), Industrial Standard Architecture (“ISA”) and Extended ISA (“EISA”) architectures, for example. In addition, the functionality provided for in the components and modules of computing system may be combined into fewer components and modules or further separated into additional components and modules.

The computing system is generally controlled and coordinated by operating system software, such as Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, Windows Vista, Windows 7, Windows 8, Unix, Linux, SunOS, Solaris, Maemeo, MeeGo, BlackBerry Tablet OS, Android, webOS, Sugar, Symbian OS, MAC OS X, or iOS or other operating systems. In other embodiments, the computing system may be controlled by a proprietary operating system. Conventional operating systems control and schedule computer processes for execution, perform memory management, provide file system, networking, I/O services, and provide a user interface, such as a graphical user interface (“GUI”), among other things.

The systemmay also include one or more multimedia devices, such as speakers, video cards, graphics accelerators, and microphones, for example. A skilled artisan would appreciate that, in light of this disclosure, a system including all hardware components, such as the processor, I/O device(s), storage device(s)that are necessary to perform the operations illustrated in this application, is within the scope of the disclosure.

In some embodiments, the processoris configured to automatically regulate the delivery of energy from the energy generation deviceto the energy delivery memberof the medical instrumentbased on one or more operational schemes. For example, energy provided to the energy delivery member(and thus, the amount of heat transferred to or from the targeted tissue) can be regulated based on, among other things, the detected temperature of the tissue being treated.

According to some embodiments, the energy delivery systemcan include one or more temperature detection devices, such as, for example, reference temperature devices (for example, thermocouples, thermistors, etc.), radiometers and/or the like.